In general, data in a computer system are handled in file units and storing and reading processes are also executed respectively in file units. Thus, in order to distinguish individual files from each other, predetermined filenames must be assigned to the respective files. In storing a file in a general application program, a user is enabled to assign an arbitrary filename to the file to be stored. Normally, the user assigns a filename that is considered to be optimal for enabling the contents, preparation date/time, etc., of the file to be stored to be ascertained readily.
There are application programs with which a function of automatically assigning a predetermined filename based on specific rules is prepared. For example, Japanese Unexamined Patent Publication No. 2001-188697 discloses an art, wherein when a file is placed in a particular folder to be monitored, a predetermined filename is assigned automatically to the file and the file is stored in a predetermined folder with a hierarchical structure.
As mentioned above, generally in saving a file, a user assigns a filename relevant to the contents of the file to be stored. Also, even in cases where a filename is automatically assigned as in the art disclosed in the above-mentioned patent Document, a filename that is somehow related to the contents of file is generally assigned. For example, in the case of a data file for an accounting process, by assigning a filename, such as “sales book for April,” it can be understood at once that the file is that of sales data for April. Likewise, in the case of a customer data file, by assigning a filename such as “company X customer file,” it can be recognized immediately that the file is that of data concerning customers of company X.
Thus, from the standpoint of a user who prepares a specific file and uses this file thereafter, assigning of a filename related to the contents of the file is extremely important for improving convenience. However, from the standpoint of security, such assignment of a filename based on convenience is not preferable. For example, the contents of a data file with the filename, “sales book of April,” can be readily inferred by any person. When a list of such filenames is seen by another user, the type of information contained in the respective files will be made known without opening of the individual files.
Recently, due to the spread of LAN, numerous computers are connected via networks and it is not infrequent that one sees a list of files prepared by another person via the networks. Thus, if there is a possibility that the contents of a file can be inferred from the filename, the possibility of encountering such damages as an important file being copied illicitly or the file itself being destroyed or deleted by a user of malicious intent becomes high. As a matter of course, setting of access rights, encryption of data files, and other arts for protecting data files from attacks by illicit means are also employed. However, in regard to the security of a filename itself, measures that have been taken up until now are by no means adequate and there are many opportunities for lists of filenames to be seen by numerous users.
An object of this invention is thus to provide a computer system enabling adequate security to be ensured even for filenames and another object is to provide such a method for storing and reading files.